The present invention relates to a data writable and readable optical disk and an optical disk apparatus for driving the optical disk.
A rewritable optical disk allows repetitive writing and reading of data at arbitrary positions. In general, data are recorded on such an optical disk in units of sectors. In this case, sector address information and error correction coded data are written in each sector.
In contrast to this, on a large-capacity rewritable optical disk called a DVD-RAM, which has recently been standardized to have a diameter of 120 mm, in order to improve the data error correction performance, data are written in units of ECC blocks each obtained by performing error correction coding throughout a plurality of sectors. The same writing (recording) method is used for a DVD-ROM as a read-only optical disk, in which data are written in units of ECC blocks each having 16 sectors each including 2,048 bytes. In the DVD-ROM, error correction coding is applied to ECC blocks and sector address information as well as data, thus realizing a structure that is highly resistant to errors.
As an optical disk on which data are recorded in units of ECC blocks in the above manner, the following optical disk has been proposed, together with an optical disk apparatus. According to this proposal, the optical disk is designed to write/read out (record/reproduce) data in units of ECC blocks each having a plurality of sectors by using at least a land track or groove track. A separation portion is formed on a groove track to be flush with a land track surface. The position information of an ECC block (information representing the address of the ECC block or the boundary between ECC blocks) is recorded as embossed pits on the boundary between this separation portion and the land track. Error correction coded data is written in each sector of the ECC block on the basis of the position information obtained from the embossed pits, together with sector address information representing the address of each sector in which data is written.
As described above, the position information of each ECC block (ECC block) is recorded as embossed pits on an optical disk. When data of each sector of the ECC block and the address information of each sector are recorded on the optical disk on the basis of this position information, the sector length on the disk changes due to variations in the rotational speed of the disk in data record/reproduce operation or decentering, or random shifts of the record position in the use of a phase change recording scheme and deterioration at the beginning/end of data occur. For this reason, to cope with random shifts and deterioration at the beginning/end of data, buffer areas are formed in units of ECC blocks. Since the buffer areas are reduced as compared with a conventional optical disk on which address information is recorded as embossed pits in units of sectors, the data record area can be increased accordingly, thus increasing the format efficiency.
In the above arrangement, however, buffer areas are formed in units of ECC blocks, and data are recorded in units of ECC blocks. For this reason, separation portions in which embossed pits are formed cannot be aligned in the radial direction of the disk, and general data record/reproduce operation is performed on tracks adjacent to tracks in which embossed pits are formed. If, therefore, the recording density increases (the track pitch decreases) in the tracking direction, crosstalk between embossed pits and record data on adjacent tracks may present a problem. When land tracks adjacent to a separation portion in which embossed pits are formed are to be reproduced, the crosstalk suppression effect in the land/groove arrangement cannot be obtained. This may affect reproduction of data.
Consider land tracks adjacent to a separation portion in which embossed pits are formed. Although a groove is present on one side, the land on the other side is flat. In this case, a problem regarding record/reproduction operation itself, i.e., a problem that an accurate shape record mark cannot be formed or the DC component of a reproduction signal may greatly change may arise, unlike the record/reproduction characteristics of a conventional land track in which groove tracks are present on the two sides of embossed pits.
In addition, since the land portion on this groove track separation portion is spread, the shape of a record mark distorts, and the mark center deviates from the center of the land track. As a result, the intensity of reflected light in reproduction operation differs from that from a land track having groove tracks on its two sides in reproduction operation. It may therefore become difficult to stably perform data record/reproduction operation.
It is an object of the present invention to provide an optical disk and optical disk apparatus which can increase a format efficiency and record data at arbitrary positions without any waste.
It is another object of the present invention to provide an optical disk apparatus which can record/reproduce data more stably on/from a land track partial region adjacent to a land portion of a groove track separation portion on an optical disk.
According to the present invention, there is provided an optical disk on/from which data can be recorded/reproduced in units of ECC blocks each constituted by a plurality of sectors, comprising a plurality of land tracks and groove tracks which are alternately arranged in a radial direction of the optical disk, a land portion which is formed on each of the groove tracks to separate a corresponding groove track of the groove tracks and is substantially flush with the land tracks, a set of embossed pits which is formed in units of ECC blocks in a boundary between the land portion and one of the land tracks located on two sides of the groove track in which the land portion is formed, and a record/reproduction interruption portion which is formed in a data area adjacent to the land portion and on the other of the land tracks located on the two sides on a side on which the set of embossed pits are not formed, no data being recorded/reproduced on/from the record/reproduction interruption portion.
In addition, according to the present invention, there is provided optical disk apparatus for recording/reproducing data on/from at least one of land and groove tracks on an optical disk in units of ECC blocks each having a plurality of sectors, comprising an optical head which records/plays back information on/from at least one of the land and groove tracks on the optical disk, and a processor which detects logical position information by which the ECC blocks are separated on the basis of position information obtained by a set of embossed pits and a record/reproduction interruption portion between the ECC blocks and performs a processing of temporarily interrupting recording/reproduction of data on/from the record/reproduction interruption portion, when data of each sector and address information of each sector are recorded/reproduced on the basis of the position information read by the optical head from the set of embossed pits formed in a boundary between each of the land tracks and a land portion for separating a corresponding one of the groove tracks on the optical disk.
When position information by which an ECC block is separated into a plurality of blocks is to be generated, a logical position at which the ECC block is separated may be located immediately before a sync pattern in a data area, immediately before sector address information, or immediately after the sector address information.
When the position information or the like of an ECC block on an optical disk is recorded as embossed pits, and the data of each sector of the ECC block and the address information of each sector are to be recorded on the basis of this position information, logical position information by which the ECC block is separated into a plurality of blocks and a record/reproduction interruption portion inserted between the plurality of separated blocks are generated on the basis of the position information of the ECC block, and recording in the record/reproduction interruption portion is temporarily interrupted. With this arrangement, buffer areas for coping with changes in actual sector length on the disk which are caused by variations in the rotational speed of the disk, decentering, and the like in data record/reproduction operation, random shifts of a record position in the use of the phase change recording scheme, and deterioration at the beginnings and end of data may be formed in units of blocks obtained by separating each ECC block.
In addition, since no data is recorded/reproduced on/from a track adjacent to a track in which embossed pits are present, this optical disk is free from any problems associated with crosstalk and data record/reproduction characteristics, and hence can increase the format efficiency as compared with a conventional rewritable optical disk.
Furthermore, according to the present invention, there is provided an optical disk apparatus for recording/reproducing information on/from an optical disk having a plurality of land tracks and groove tracks which are alternately arranged adjacent to one another, and a plurality of land portions which are substantially flush with the land tracks and separate the groove tracks, respectively, and a plurality of sets of embossed pits each which are formed in a boundary between one of the land tracks located on two sides of each of the groove tracks in which the land portions are formed, respectively, and a corresponding one of the land portions and represent position information, comprising a driving section for rotating/driving the optical disk, an optical head which performs selectively recording and reproducing information on/from the optical disk by irradiating the optical disk with a light beam, and a control section which controls tracking so that a position of the light beam is fixed to a predetermined position in a radial direction of the optical disk in a period during which the light beam is positioned in a partial portion of one of the land tracks that is adjacent to another one of the land portions that is on a side opposite to a side of the boundary on which the embossed pits are formed.
More specifically, the operation state control section controls the tracking control system to fix the position of a light beam in the radial direction of the disk to a predetermined position (e.g., a position at which the light beam is offset to the groove track adjacent to the land track partial region by a predetermined amount) in a period during which the light beam is positioned in the land track partial region adjacent to the groove track separation portion on the opposite side to the side where the embossed pits are formed. In addition, during this period, the operation state control section performs (a) control to decrease the intensity of the record light beam in the recording system by a predetermined value, or (b) control to decrease at least one of the intensity of a reproduction light beam in the reproduction system and a gain and DC offset amount to be provided for a reproduction signal by a predetermined value.
If the position of a light beam in the radial direction of the disk is fixed in the land track partial region adjacent to the groove track separation portion on the opposite side to the side where the embossed pits are formed, this operation can prevent disturbance of tracking servo control. In addition, since the light beam passes through the land track partial region in a short period of time, even if the position of the light beam is fixed in the radial direction of the disk, no problem arises. Stable record/reproduction operation can therefore be performed even in such a land track partial region.
In this case, the position of a light beam may be fixed in the radial direction of the disk immediately before it reaches the land track partial region. However, when the position of the light beam is fixed, the light beam is preferably offset, by a predetermined amount, to the groove track adjacent to the land track partial region.
Since one side of this land track partial region in the radial direction of the disk is a land portion of a groove track separation portion, the land track partial region easily diffuses heat generated upon irradiation of a light beam as compared with a general land track having the groove tracks formed on its two sides. The record mark therefore tends to distort. This distortion of the record mark tends to lead to a change in shape and an increase in the size of the mark. For this reason, the distortion of the record mark can be reduced by decreasing the intensity of a record light beam in the land track partial region. In this case, the distortion of the record mark can be prevented more effectively by offsetting the light beam to the groove track adjacent to the land track partial region.
In addition, the record mark in such a land track partial region tends to distort. For this reason, in reproduction of data from the land track partial region, the reflected light intensity increases due to the distortion of the record mark and the distortion of a reproduction signal increases as compared with reproduction of data from other areas. In consideration of the above situation, in order to prevent this problem, in the land track partial region, the intensity of a reproduction light beam is set lower than that in reproduction of data from other general land tracks or groove tracks. With this control, the distortion of the reproduction signal due to the distortion of the record mark can be reduced.
In addition, in such a land track partial region, the mark center deviates from the track center due to the distortion of the record mark, resulting in an increase in the distortion of the reproduction signal. Such distortion of the reproduction signal can be reduced by offsetting the light beam to the groove track adjacent to the land track partial region.
Obviously, the same effect as described above can be obtained by decreasing the gain or DC offset amount to be provided for a reproduction signal in the amplifier in the signal processing system instead of decreasing the intensity of a reproduction light beam.
In the present invention, a control position at which the operation states of the recording or reproduction system are switched, i.e., the position of a land track partial region adjacent to a groove track separation portion on the opposite side to the side where embossed pits are formed (in other words, the position of a land track partial region which is adjacent to a large portion of a groove track separation portion and does not share embossed pits) may be managed in accordance with position information stored in the memory in advance or may be calculated.
As described above, according to the present invention, the position of a land track partial region which is adjacent to a land portion of a groove track separation portion and does not share embossed pits 16 is obtained, and the above switching control is performed on the basis of the obtained position, thereby performing better record/reproduction operation in this land track partial region.